Recombinant Schizosaccharomyces pombe Uncharacterized protein C18G6.10 (SPAC18G6.10)

What is SPAC18G6.10 and what is its localization in Schizosaccharomyces pombe?

SPAC18G6.10, also known as Lem2 or Heh1, is a LEM domain protein in Schizosaccharomyces pombe (fission yeast) that localizes specifically to the Inner Nuclear Membrane (INM) . Fluorescence microscopy reveals that Lem2, when tagged with GFP, shows characteristic nuclear periphery localization with non-uniform dots, typical of nuclear envelope proteins .

Lem2 is a paralogue of Saccharomyces cerevisiae Heh1 and Heh2 proteins, which also localize to the INM . This localization suggests its involvement in nuclear envelope organization and stability. Studies have demonstrated its importance as a nuclear envelope marker for visualizing nuclear dynamics during various cellular processes .

How is SPAC18G6.10 categorized functionally in genomic databases?

SPAC18G6.10/Lem2 is functionally categorized in several ways:

In genome-wide screens, Lem2 has been implicated in multiple cellular processes including nuclear organization, retrotransposon integration, and vesicular transport . Its classification reflects its multifunctional role at the interface of the nuclear envelope and chromatin .

What are the optimal conditions for expressing recombinant SPAC18G6.10 protein?

For optimal expression of recombinant SPAC18G6.10/Lem2 protein, consider the following methodology:

• Expression System: E. coli has been successfully used for expression of the full-length protein (amino acids 1-688) with an N-terminal His tag .

• Protein Production:

  • Express as a fusion protein with His-tag for purification

  • Typical yield should achieve >85-90% purity as determined by SDS-PAGE

  • Final product is generally provided as a lyophilized powder

• Storage and Handling:

  • Store lyophilized protein at -20°C/-80°C upon receipt

  • Aliquot for multiple use to avoid repeated freeze-thaw cycles

  • Reconstitute in deionized sterile water to 0.1-1.0 mg/mL

  • Add 5-50% glycerol for long-term storage (recommended final concentration is 50%)

  • Store working aliquots at 4°C for up to one week

• Buffer Composition:

  • Reconstitution in Tris/PBS-based buffer with 6% Trehalose, pH 8.0

These conditions have been validated for producing functional recombinant SPAC18G6.10 suitable for biochemical and structural studies.

What experimental approaches can be used to characterize SPAC18G6.10 function?

Several experimental approaches can be employed to characterize SPAC18G6.10/Lem2 function:

• Genetic Manipulation Approaches:

  • Gene deletion (lem2Δ) to observe phenotypic changes

  • GFP tagging under natural promoter for localization studies

  • Point mutations in specific domains to assess functional contributions

• Microscopy Techniques:

  • Fluorescence microscopy for localization studies

  • Electron cryotomography for ultrastructural analysis

  • Live-cell imaging to track dynamics during cell cycle

• Biochemical Approaches:

  • Co-immunoprecipitation to identify interaction partners

  • Chromatin immunoprecipitation (ChIP) to identify DNA associations

  • In vitro binding assays with purified components

• Quantitative Analysis:

  • Fluorescence intensity measurements to determine protein abundance

  • FRAP (Fluorescence Recovery After Photobleaching) to assess mobility

  • Single-molecule tracking to analyze dynamics

• Functional Assays:

  • Retrotransposon integration assays

  • Nuclear envelope stability assessments

  • Nuclear-cytoplasmic transport assays

These approaches provide complementary data that together can elucidate the multifaceted roles of SPAC18G6.10/Lem2 in nuclear organization and function.

How should researchers design experiments to avoid artifacts when studying SPAC18G6.10?

When designing experiments to study SPAC18G6.10/Lem2, researchers should implement the following controls and considerations to avoid artifacts:

• Expression Level Controls:

  • Express the protein under its natural promoter to maintain physiological levels

  • Avoid overexpression which can cause mislocalization and function perturbation

  • Compare results with genomically tagged versus plasmid-expressed protein

• Tag Selection and Positioning:

  • Test both N- and C-terminal tags to determine optimal configuration

  • Use smaller tags (FLAG, HA) for interaction studies to minimize interference

  • Verify that tagged protein complements deletion phenotypes

• Appropriate Controls:

  • Include untagged strains as negative controls

  • Use known nuclear envelope proteins as positive controls

  • Compare with other LEM domain proteins to distinguish specific vs. general effects

• Validation Approaches:

  • Confirm key findings using multiple independent methods

  • Perform rescue experiments with wild-type protein to verify specificity

  • Use orthogonal techniques to verify interactions or localizations

• Physiological Considerations:

  • Assess function across different cell cycle stages

  • Test under various stress conditions (mechanical, temperature, osmotic)

  • Consider the impact of growth conditions on nuclear organization

By implementing these experimental design principles, researchers can generate more reliable and physiologically relevant data on SPAC18G6.10/Lem2 function.

What is the role of SPAC18G6.10 in nuclear envelope organization and function?

SPAC18G6.10/Lem2 plays a critical role in nuclear envelope organization and stability:

• Structural Integrity: Lem2 contributes to nuclear envelope resilience against mechanical forces. Studies using mCherry-tagged Lem2 revealed its role in maintaining nuclear envelope integrity when subjected to forces from microtubule bundles .

• Nuclear Morphology: When other nuclear envelope proteins (e.g., Ima1) are deleted, pronounced nuclear envelope deformations occur, suggesting Lem2 works cooperatively with other proteins to maintain nuclear shape .

• Chromatin Interactions: As a LEM domain protein, Lem2 likely mediates interactions between the nuclear envelope and chromatin, contributing to genome organization and stability .

• Nuclear Pore Complex Association: While not a core component of the nuclear pore complex (NPC), Lem2 associates with the nuclear periphery in a pattern similar to nucleoporins, suggesting potential functional interactions with the NPC .

Studies comparing wild-type and mutant cells indicate that disruption of Lem2 function can lead to alterations in nuclear envelope morphology, particularly under conditions of mechanical stress , highlighting its importance in maintaining nuclear integrity.

How does SPAC18G6.10 relate to retrotransposon integration in the genome?

A genome-wide screen identified SPAC18G6.10/Lem2 among 61 host factors that promote retrotransposon integration in fission yeast . This connection reveals an unexpected role for nuclear envelope proteins in genome dynamics:

• Integration Mechanism: As a nuclear envelope protein, Lem2 may provide access points for retrotransposon integration machinery to chromatin .

• Experimental Evidence: The screen employed a combination of assays to detect defects in integration, distinguishing between effects on integration versus earlier steps in retrotransposition .

• Functional Categorization: Lem2 was categorized among vesicle transport factors affecting integration, alongside other proteins involved in ER-to-Golgi transport and ESCRT complexes .

The table below shows other proteins identified in the same functional category:

This relationship between nuclear envelope proteins and retrotransposon integration represents an important area for further investigation, potentially revealing new insights into genome evolution and stability.

What phenotypes result from SPAC18G6.10 deletion or mutation?

Based on research findings, SPAC18G6.10/Lem2 deletion or mutation results in several characteristic phenotypes:

These phenotypes highlight the multifaceted roles of Lem2 in maintaining nuclear structure and function, with downstream effects on multiple cellular processes.

How can advanced imaging techniques be applied to study SPAC18G6.10 dynamics?

Advanced imaging techniques offer powerful approaches for studying SPAC18G6.10/Lem2 dynamics in living cells:

• Super-Resolution Microscopy:

  • Technique: STED, PALM, or STORM microscopy

  • Application: Resolve Lem2 distribution at the nuclear envelope with nanometer precision

  • Advantage: Overcomes the diffraction limit of conventional microscopy to reveal detailed spatial organization

• Live-Cell Dynamics:

  • Technique: FRAP (Fluorescence Recovery After Photobleaching)

  • Application: Measure mobility and turnover rate of GFP-tagged Lem2

  • Methodology: Photobleach a region of the nuclear envelope and monitor fluorescence recovery

• Protein-Protein Interactions:

  • Technique: FRET (Förster Resonance Energy Transfer)

  • Application: Detect interactions between Lem2 and other proteins in real-time

  • Implementation: Tag Lem2 and potential partners with appropriate fluorophore pairs

• Single-Molecule Analysis:

  • Technique: Single-particle tracking with photoactivatable fluorescent proteins

  • Application: Track individual Lem2 molecules to analyze diffusion and binding

  • Benefit: Reveals heterogeneity in behavior not apparent in population measurements

• Multi-dimensional Imaging:

  • Technique: Lattice light-sheet microscopy

  • Application: Capture 3D dynamics with minimal phototoxicity

  • Advantage: Ideal for long-term imaging during cell division or nuclear reorganization

• Correlative Approaches:

  • Technique: Correlative Light and Electron Microscopy (CLEM)

  • Application: Correlate fluorescence of Lem2-GFP with ultrastructural features

  • Benefit: Bridges the resolution gap between light and electron microscopy

Implementation of these advanced imaging approaches requires careful consideration of tagging strategies, expression levels, and image analysis methods to generate reliable and physiologically relevant data.

How conserved is SPAC18G6.10 function across different species?

SPAC18G6.10/Lem2 belongs to the evolutionarily conserved family of LEM domain proteins found across eukaryotes, with varying degrees of functional conservation:

• Yeast Orthologs:

  • S. cerevisiae: Heh1 and Heh2 are functional paralogs that localize to the inner nuclear membrane

  • Conservation: Core functions in nuclear organization appear conserved between budding and fission yeast

• Nematode (C. elegans):

  • LEM-2 is a direct ortholog (as mentioned in search result )

  • Function: Nuclear envelope organization and chromatin interactions

  • Available tools: Anti-Caenorhabditis elegans lem-2 polyclonal antibodies for experimental studies

• Mammals/Humans:

  • Multiple LEM domain proteins: Emerin, LAP2, and MAN1

  • Disease relevance: Mutations in human LEM domain proteins are associated with diseases like Emery-Dreifuss muscular dystrophy

  • Functional aspects: Human orthologs share roles in nuclear structure and chromatin organization

Comparative functional studies using complementation experiments (expressing human LEM domain proteins in lem2Δ S. pombe cells) could reveal the extent of functional conservation and species-specific adaptations.

How can researchers quantitatively analyze SPAC18G6.10 abundance and distribution?

Quantitative analysis of SPAC18G6.10/Lem2 abundance and distribution requires rigorous methodological approaches:

• Fluorescence Intensity Measurement:

  • Methodology: As described in search result , fluorescence intensity of GFP-tagged Lem2 can be measured in living cells

  • Quantification: Express values relative to other nuclear envelope proteins

  • Data presentation: Generate tables of relative abundance similar to those in result

• Western Blot Analysis:

  • Approach: Use anti-Lem2 antibodies for protein quantification

  • Controls: Include loading controls and calibration standards

  • Analysis: Densitometry to quantify expression levels under different conditions

• Subcellular Fractionation:

  • Method: Separate nuclear envelope from other cellular compartments

  • Quantification: Measure Lem2 abundance in different fractions

  • Validation: Use markers for different compartments to confirm fractionation quality

• Image Analysis Techniques:

  • Line scan analysis: Measure fluorescence intensity across the nuclear envelope

  • 3D reconstruction: Analyze the entire nuclear envelope distribution pattern

  • Colocalization analysis: Quantify overlap with other nuclear envelope markers

• Mass Spectrometry-Based Quantification:

  • Approach: Targeted proteomics using labeled reference peptides

  • Data acquisition: Selected or parallel reaction monitoring (SRM/PRM)

  • Analysis: Absolute quantification of Lem2 molecules per cell

Example quantification approach based on fluorescence intensity:

These quantitative approaches provide robust data for comparing Lem2 expression and distribution under different experimental conditions or genetic backgrounds.

How can contradictory findings about SPAC18G6.10 function be reconciled?

When confronted with contradictory findings regarding SPAC18G6.10/Lem2 function, researchers should consider several strategies for reconciliation:

• Methodological Differences:

  • Analyze differences in experimental approaches

  • Compare expression systems: genomic tagging vs. plasmid expression

  • Evaluate tag positions and their potential impact on function

  • Consider strain background differences

• Context-Dependent Functions:

  • Assess cell cycle stage specificity of observations

  • Compare growth conditions and stress responses

  • Examine potential redundancy with other nuclear envelope proteins

  • Consider interaction with different partners under various conditions

• Quantitative Analysis:

  • Compare quantitative vs. qualitative assessments

  • Analyze statistical power of different studies

  • Consider threshold effects in interpreting phenotypes

  • Perform meta-analysis of multiple datasets

• Integrative Approaches:

  • Combine genetics, cell biology, and biochemical data

  • Use computational modeling to integrate diverse datasets

  • Apply systems biology approaches to place contradictions in context

  • Consider evolutionary perspectives across species

• Validation Experiments:

  • Design experiments specifically to address contradictions

  • Use orthogonal techniques to verify key findings

  • Perform epistasis analysis to place gene functions in pathways

  • Conduct rescue experiments with defined mutants

By systematically addressing potential sources of contradiction, researchers can develop more nuanced models of Lem2 function that accommodate seemingly disparate observations.

What are the key considerations for experimental design when investigating SPAC18G6.10 interactions?

When designing experiments to investigate SPAC18G6.10/Lem2 interactions, researchers should incorporate these key considerations:

• Experimental Design Principles:

  • Control variables: Maintain consistent growth conditions, strain backgrounds, and expression levels

  • Independent variables: Clearly define manipulated factors (e.g., Lem2 mutations, interaction partner deletions)

  • Dependent variables: Specify measurable outcomes (e.g., co-immunoprecipitation efficiency, localization changes)

  • Replication: Include biological and technical replicates for statistical validity

• Protein Expression Strategies:

  • Expression under native promoter to maintain physiological levels

  • Consider inducible systems for controlled expression

  • Compare genomic integration versus plasmid expression

  • Validate functionality of tagged constructs

• Interaction Detection Methods:

  • Co-immunoprecipitation with appropriate controls

  • Yeast two-hybrid with proper bait and prey controls

  • Proximity labeling (BioID, APEX) for identifying neighborhood proteins

  • FRET/BRET for detecting direct interactions in living cells

• Control Experiments:

  • Tag-only controls to identify tag-mediated interactions

  • Domain deletion/mutation controls to map interaction interfaces

  • Competition assays to validate specificity

  • Reciprocal tagging to confirm interactions

• Membrane Protein Considerations:

  • Optimize lysis conditions to solubilize membrane proteins

  • Consider using crosslinking to preserve transient interactions

  • Include detergent controls to distinguish direct vs. membrane-mediated interactions

  • Account for nuclear envelope topology in interpreting results

By incorporating these considerations into experimental design, researchers can generate more reliable and interpretable data on Lem2 interactions, advancing understanding of its functions in nuclear organization and cellular processes.

How might research on SPAC18G6.10 contribute to understanding human disease mechanisms?

Research on SPAC18G6.10/Lem2 has significant potential to advance understanding of human disease mechanisms:

• Relevance to Human Genetics:

  • Over 70% of S. pombe protein-coding genes have human orthologs

  • More than 1500 of these are associated with human disease

  • LEM domain proteins in humans are linked to several disorders, including Emery-Dreifuss muscular dystrophy

• Nuclear Envelope Diseases:

  • Laminopathies: Conditions affecting nuclear lamina and associated proteins

  • Understanding Lem2 function could provide insights into disease mechanisms

  • S. pombe as a model system allows genetic manipulation not possible in patient cells

• Cancer Biology:

  • Nuclear envelope disruption is a hallmark of many cancers

  • Lem2's role in chromatin organization may relate to genomic instability in cancer

  • Retrotransposon integration, influenced by Lem2 , is often dysregulated in cancer

• Cell Division Defects:

  • Abnormal nuclear morphology is associated with many diseases

  • Lem2's function in maintaining nuclear envelope integrity during cell division may inform understanding of disease-related mitotic defects

• Translational Potential:

  • Drug screening in S. pombe with Lem2 mutations could identify compounds that rescue phenotypes

  • Identification of Lem2 interaction partners may reveal novel therapeutic targets

  • CRISPR-based approaches targeting human orthologs could be informed by S. pombe studies

The simplicity of fission yeast combined with conservation of key pathways makes research on Lem2 a valuable approach for understanding fundamental mechanisms that may be dysregulated in human disease.

What emerging technologies might advance our understanding of SPAC18G6.10 function?

Several emerging technologies have the potential to significantly advance understanding of SPAC18G6.10/Lem2 function:

• Genome Editing Technologies:

  • CRISPR-Cas9 for precise genome modifications and base editing

  • Implementation: Generate allelic series of Lem2 mutations

  • Advantage: Examine effects of specific domains or residues without overexpression artifacts

• Proximity Proteomics:

  • BioID or APEX2 fusion proteins for in vivo proximity labeling

  • Implementation: Map the protein neighborhood of Lem2 at the nuclear envelope

  • Advantage: Identifies transient or weak interactions missed by traditional methods

• Single-Cell Technologies:

  • Single-cell RNA-seq and proteomics

  • Implementation: Analyze cell-to-cell variability in Lem2 expression and function

  • Advantage: Reveals heterogeneity masked in population averages

• Cryo-Electron Tomography:

  • In situ structural analysis of macromolecular complexes

  • Implementation: Visualize Lem2 in its native nuclear envelope context

  • Advantage: Provides structural insights at molecular resolution

• Integrative Modeling:

  • Combine structural, genomic, and imaging data

  • Implementation: Generate comprehensive models of Lem2 function at the nuclear envelope

  • Advantage: Integrates diverse datasets into coherent functional models

• Optogenetic Approaches:

  • Light-inducible protein interactions or activity modulation

  • Implementation: Control Lem2 interactions or conformations with spatial and temporal precision

  • Advantage: Allows dynamic perturbation of protein function in living cells

• AI-Driven Protein Structure Prediction:

  • AlphaFold2 and related tools for structure prediction

  • Implementation: Generate structural models of Lem2 and its complexes

  • Advantage: Provides structural insights for proteins recalcitrant to experimental structure determination

These emerging technologies, particularly when used in combination, have the potential to address long-standing questions about Lem2 function and generate new hypotheses for experimental testing.

How should researchers integrate multi-omics data to develop comprehensive models of SPAC18G6.10 function?

Developing comprehensive models of SPAC18G6.10/Lem2 function requires sophisticated integration of multi-omics data:

• Data Collection Strategies:

  • Genomics: Genome-wide screens for genetic interactions with lem2Δ

  • Transcriptomics: RNA-seq comparing wild-type and lem2Δ cells under various conditions

  • Proteomics: Mass spectrometry to identify Lem2 interactors and post-translational modifications

  • Metabolomics: Metabolic profiling to identify downstream effects of Lem2 disruption

  • Phenomics: Systematic phenotypic characterization across conditions

• Integration Approaches:

  • Network analysis: Construct protein-protein interaction networks centered on Lem2

  • Pathway enrichment: Identify biological processes affected by Lem2 disruption

  • Multi-omics correlation: Find concordance between transcriptomic and proteomic changes

  • Temporal analysis: Track dynamic changes across omics layers during cellular processes

• Computational Methods:

  • Machine learning: Train predictive models of Lem2 function based on omics data

  • Causal inference: Distinguish direct vs. indirect effects of Lem2 disruption

  • Bayesian approaches: Integrate prior knowledge with new experimental data

  • Boolean network modeling: Capture regulatory relationships involving Lem2

• Validation Strategies:

  • Targeted experiments to test model predictions

  • CRISPR screens to validate potential pathways

  • Comparative analysis across species to identify conserved mechanisms

  • Perturbation experiments to test model robustness

• Data Visualization and Sharing:

  • Interactive visualizations of integrated networks

  • Public database submission of raw data

  • Development of web resources for the community

  • Standardized reporting of methods for reproducibility

By implementing these strategies, researchers can develop nuanced, systems-level understanding of Lem2 function that captures its roles across multiple cellular processes and contexts.

What are the most promising directions for future research on SPAC18G6.10?

Based on current knowledge and technological capabilities, several promising directions for future SPAC18G6.10/Lem2 research emerge:

• Mechanistic Understanding:

  • Detailed characterization of Lem2's role in nuclear envelope stability

  • Molecular basis of Lem2's contribution to retrotransposon integration

  • Structural studies of Lem2 interactions with chromatin and other nuclear envelope proteins

• Systems Integration:

  • Positioning Lem2 within the broader nuclear organization network

  • Identifying condition-specific functions across the cell cycle and stress responses

  • Understanding crosstalk between Lem2 and other cellular pathways

• Evolutionary Perspectives:

  • Comparative analysis of Lem2 function across species

  • Identification of conserved vs. species-specific adaptations

  • Implications for evolution of nuclear organization

• Translational Applications:

  • Relevance to understanding human LEM domain protein functions

  • Potential as a target for manipulating nuclear organization

  • Applications in synthetic biology for nuclear engineering

• Technology Development:

  • Development of Lem2-specific probes and sensors

  • Application of emerging technologies to visualize Lem2 dynamics

  • High-throughput approaches to map Lem2 genetic and physical interactions

These research directions, pursued with rigorous methodology and cutting-edge technologies, promise to advance understanding of this important but still partially characterized protein in nuclear organization and function.

How can researchers overcome current technical limitations in studying SPAC18G6.10?

Researchers face several technical challenges when studying SPAC18G6.10/Lem2 that can be addressed through innovative approaches:

• Membrane Protein Analysis Challenges:

  • Challenge: Difficult solubilization and purification of membrane proteins

  • Solution: Develop optimized detergent conditions or nanodiscs for maintaining native structure

  • Alternative: Focus on soluble domains for initial structural and interaction studies

• Dynamic Range Limitations:

  • Challenge: Low abundance of Lem2 relative to highly expressed proteins

  • Solution: Implement targeted proteomics approaches (SRM/PRM)

  • Alternative: Use enrichment strategies prior to analysis

• Temporal Resolution:

  • Challenge: Capturing rapid dynamics during nuclear envelope reorganization

  • Solution: Implement high-speed imaging with minimal phototoxicity

  • Alternative: Develop synchronization methods to enrich for specific cell cycle stages

• Spatial Resolution:

  • Challenge: Distinguishing inner nuclear membrane from other components

  • Solution: Apply super-resolution microscopy techniques

  • Alternative: Use correlative light and electron microscopy approaches

• Functional Redundancy:

  • Challenge: Compensatory mechanisms masking phenotypes in single mutants

  • Solution: Generate multiple knockouts of related genes

  • Alternative: Use acute depletion strategies (auxin-inducible degron) to prevent adaptation

• Experimental Variability:

  • Challenge: Ensuring reproducibility across experiments and labs

  • Solution: Develop standardized protocols and reference materials

  • Alternative: Implement robust statistical approaches and increased replication